Extracellular fatty acid binding protein (Ex-FABP) modulation by inflammatory agents: "physiological" acute phase response in endochondrol bone formation

Ex-FABP, extracellular fatty acid binding protein, is a 21 kDa lipocalin ex pressed in hypertrophic cartilage, muscle and heart during chick embryo dev elopment and in granulocytes. Ex-FABP synthesis was increased in chondrocyt e and myoblast cultures by inflammatory agents (LPS; IL6) and repressed by antiinflammatory agents. Expression of Ex-FABP and specific gelatinases is paralleled in hypertrophic cartilage; LPS specifically induced high molecul ar weight gelatinase (> 200 kDa), LPS-treated hypertrophic chondrocytes sho wed increased chemotactic activity for endothelial cells paralleled by incr eased expression of transferrin. A high amount of Ex-FABP was expressed in adult pathological cartilage both in dyschondroplastic and osteoarthritic chickens. Controls were negative. Ex-FABP could represent a stress protein physiologically expressed in tissu es where active remodelling is taking place during development and in tissu es characterized by an acute phase response due to pathological conditions. We also suggest that during endochondral bone formation other responses ch aracteristic of a local inflammatory status, such as gelatinase production and angiogenic factor secretion, are "physiologically" activated.